Conventional streamer systems or ocean bottom cable systems have been the traditional ocean seismic imaging systems. However, these systems ordinarily record narrow azimuth data. Complex geological formations such as the salt bodies of the Gulf of Mexico have resulted in the need of more sophisticated subsurface images.
A current solution is the use of all azimuth illumination and data acquisition. One example of all azimuth data acquisition uses autonomous ocean bottom nodes. Nodes are independent seismometers. In the typical application, they are battery-powered with precise clocks for time synchronization. In operation, the nodes remain on the seafloor for an extended period of time for the recording of acoustic waves coming from a source vessel at the surface and returning energy from formations below the sea bed. Ocean Bottom Seismometers (OBS) are used for the recording of seismic data on the sea-floor. They are self contained recording stations comprising, geophone and hydrophone sensors, recording unit, and reference clock and power source. They are intended for long term autonomous acquisition for up to 6 months. Data are accessed after recovery of the units. OBS nodes can be used for passive seismic monitoring or for recording seismic energy generated by acoustic sources. The latter method can be used for oil and gas exploration or for production monitoring. They are retrieved, at which time, the data are downloaded and batteries may be replaced or recharged ready for the next deployment.
The inventors have developed an improved autonomous ocean bottom node seismic recording device having an integrated modular design and one or more features that assist coupling of the unit to the sea floor and improve the azimuthal fidelity of seismic signal measurement (vector fidelity).